This invention relates to the liquefication of animal tissues of all types, and single cell microorganisms. More particularly, it relates to a dual stage treatment of such materials, first with heat and under alkaline conditions, and then with proteolytic enzymes with heat and under alkaline conditions, to provide products containing protein hydrolysates, lipids and phosphorous in solution useful as feed supplements and/or as fertilizers.
While it is well known that many protein-containing materials of plant and animal origin (including microorganisms) can be partially or totally solubilized by treatment with caustic soda, or other strong alkalies, it requires high concentration of the alkaline substance and extensive heating, usually at the boiling point. The degradation of the protein which occurs often leads to isomerization of the amino acids, deamination, and the loss of sulfur from sulfur-containing amino acids. The nutritional value of the materials is therefore substantially reduced.
It is also known that many protein-containing substances can be hydrolyzed to some extent, and therefore partially liquefied by the use of available proteolytic enzymes now in commerce. In many cases, the degree of digestion is incomplete. Many types of cells cannot be ruptured by this approach. Due to inactivation of the enzyme, the digestions usually must be carried out at ambient temperatures of 34.degree.-45.degree. C. At higher temperatures, inactivation of the enzymes can occur. Very long periods of digestion may produce useful products. To accelerate the action, larger amounts of enzyme may be used to help drive the reaction. In some cases it may be possible to achieve complete liquefication; however, such a process would not be economical or practical.
The products which result from the above manipulations are known as peptones, peptides, and if hydrolysis has proceeded far enough, free amino acids. The nature of the products will depend upon the enzymes used. Such products currently are used in feed, as fermentation ingredients, in foods, and in bacteriological media.
Typical of the prior art patents in this area are two patents to Keil, et al., U.S. Pat. Nos. 2,431,256 and 2,477,255. These patents describe a protein hydrolysis under severe conditions of alkalinity and termperature which result in a degradation of the amino acid quality of the end products. Sato, et al., U.S. Pat. No. 3,891,770, describes a waste water treatment procedure in which protein and fat are concentrated with the assistance of a polyacrylate precipitating agent to prepare a froth. The patent to Bosund, et al., U.S. Pat. No. 3,924,005, describes a totally enzymatic process for solubilizing fish proteins. In contrast to these patents and other prior art, the present process utilizes a mild and rapid saponification at pH about 12, followed by enzymatic hydrolysis that results in a liquid product soluble across the full pH range, and in which the amino acids, lipids and phosphorous have not been harmed by the treatment, but remain in a metabolically useful form.